Fiftysomething Diet: Vitamin D for Healthier Knees

When cranky, painful knees turn out to be the beginnings of the “wear and tear” joint disease called osteoarthritis, it’s disheartening to hear doctors tell you there is no cure.

The good news, however, is that there appears to be a diet strategy that slows down progression of osteoarthritis. At least that’s the word from researchers at Tufts University.

After four years of following 418 volunteers (a subset of participants in a large study called the Osteoarthritis Initiative), they noticed participants with low vitamin D levels had more than double the risk of their knee osteoarthritis worsening during the study than volunteers with healthy levels of vitamin D.

The scientists concluded that not only is vitamin D deficiency a risk factor for increased knee osteoarthritis progression, but that an adequate dietary intake might be beneficial to anyone with the disease.

It’s certainly not the first time researchers have found a strong link between osteoarthritis and vitamin D deficiency. In fact, Greek researchers published a study earlier this year finding that four out of five patients with osteoarthritis are vitamin D deficient, even though they live in one of the most sun-drenched parts of the world.

Health experts are beginning to wonder if these findings make a strong case for searching out vitamin-D rich foods like salmon or eggs, or taking a vitamin supplement, to help osteoarthritis damaged knees.

After reviewing much of the research on Vitamin D and health back in 2010, the Institute of Medicine set daily requirements for this nutrient at 600 international units (IU) for everyone under age 70. (After 70, the recommended RDA jumps up to 800 IU.)

Unfortunately, if you’re 50 or older, chances are good you’re not meeting these target levels, for a couple of key reasons.

Older adults tend to spend more time indoors and so have less exposure to the “sunshine vitamin;" older skin is not as adept at manufacturing vitamin D after skin exposure to the sun. And older adults are more likely to take in too little of the vitamin, either from supplements or from the narrow list of foods that contain the nutrient.

As any good health professional will tell you, food is usually the best way to get most nutrients. But that’s not the case with vitamin D, says Dr. Howard Lewine, a practicing internist at Brigham and Women’s Hospital in Boston, Mass., and chief medical editor at Harvard Health Publications.

“Only a few foods — salmon, tuna, sardines, milk, fortified cereals and some types of mushroom — can give you more than 100 IU” of the vitamin per serving, he says. So Lewine suggests that taking “a supplement containing 400 to 1,000 IU is safe, inexpensive insurance.”

On the other hand, it doesn’t hurt to include vitamin-D rich foods on the menu whenever possible. Fatty fish like salmon are the richest source. A 3-ounce cooked portion of sockeye salmon has 447 international units (IU) of vitamin D or about 112 percent of your daily requirement. Two large eggs contains 82 IU or about 20 percent of daily needs. A cup of vitamin D fortified milk nets you 115 to 124 IU.

If you’re looking to do even more to help prevent or slow down the progression of osteoarthritis, the Arthritis Foundation suggests taking a look at your overall diet quality.

While there is no “anti-arthritis” diet, there are two key diet strategies fiftysomethings may want to keep in mind to promote knee joint health.

First, eat less of the foods that promote inflammation, such as saturated fats, trans fats, salt and sugar. That last ingredient is probably one of the worst offenders because high levels of sugar in the blood can stimulate the production of inflammatory substances that damage joints.

Second, eat less of the foods that lead to weight gain. It’s no secret that extra pounds put more pressure on joints. But a 2014 Australian study finds that weight gain worsens knee symptoms in obese adults with osteoarthritis and increases the loss of medial knee cartilage.

Weight loss, on the other hand, equates to less cartilage loss and improved knee symptoms.